Actuation Time Research Articles

Design of a Metered-Dose Inhaler Actuated by Shape Memory Alloy

The global prevalence of asthma and chronic obstructive pulmonary disease (COPD) is on the order of hundreds of millions of individuals. The most common treatment approach is to take a self-administered inhaled medication. This study focuses on pressurized metered-dose inhalers (MDIs) where, unfortunately, rates of mishandling and misuse are extremely high and lead to improper treatment. One significant challenge results from the timing miscoordination of the medicine dispersion and inhalation breath. To address this, this study demonstrates the feasibility of automating the timing of the medicine dispersion by integrating a shape memory alloy (SMA) actuator and a differential pressure sensor into the casing of a traditional MDI. The approach is to measure the vacuum pressure created by an inspiratory breath, evaluate criteria indicating an acceptable breath, and if those criteria are met, heat the SMA actuator to depress the cartridge and disperse medicine. To meet actuation requirements and reliably depress the inhaler cartridge, two concepts for configuring an SMA wire were designed and compared with respect to complexity, actuation timing, and energy consumption. The proposed concept was able to disperse medicine in 263 ms, averaged over 100 actuations on a single battery charge, facilitating the early dispersion of medicine during an inhalation breath. By describing the design process of an SMA-actuated MDI that does not result in a significant increase of its weight or size, this study provides a practical technological approach for reducing the improper treatment of asthma and COPD due to timing miscoordination.

Dehydration-induced folding of poly(ε-caprolactone)-agarose hydrogel composites

Materials that can be actuated by external stimuli are of particular interest for the manufacturing of interactive objects. Such materials open the possibility to change the shape of objects in response to external conditions, such as humidity. Biocompatible and biodegradable materials like agarose and poly(ε-caprolactone) (PCL) are of high interest as they can lead to objects able to interact with biological systems for instance for the implantation of small print-size object that could deploy under physiological conditions. However, these are not typical candidate materials for the manufacturing of interactive objects. In this study, a composite material was made by reinforcing agarose hydrogels with PCL scaffolds, and upon dehydration a predictable folding of the composites was obtained. More interestingly, this folding is shown to be reversible upon rehydration. Starting with a simple rectangular shape, we designed foldable structures with 1, 3 and 4 hinges. Subsequently, a triangular shape that automatically folds into a pyramid was manufactured. The actuation time, actuation intensity and mechanical properties were measured and correlated with scaffold design.

Evaluation of an intraventricular balloon pump for short-term support of patients with heart failure.

The high cost of ventricular assist devices results in poor cost-effectiveness when used as a short-term bridging solution, thus a low-cost alternative is desirable. The present study aimed to develop an intraventricular balloon pump (IVBP) for short-term circulatory support, and to evaluate the effect of balloon actuation timing on the degree of cardiac support provided to a simulated in vitro severe heart failure (SHF) patient. A silicone IVBP was designed to avoid contact with internal left ventricular (LV) features (ie, papillary muscles, chordae, aortic, and mitral valves) based on LV computed tomography data of 10 SHF patients with dilated cardiomyopathy. The hemodynamic effects of varying balloon inflation and deflation timing parameters (inflation duty [D] and end-inflation point [σ]) were evaluated in a purpose-built systemic mock circulatory loop. Three IVBP actuation timing categories were defined: co-, transitional, and counterpulsation. Compared to the SHF baseline, co-pulsation increased aortic flow from 3.5 to 5.2L/min, mean arterial pressure from 72.1 to 94.8mmHg and ejection fraction from 14.4% to 21.5%, while mean left atrial pressure decreased from 14.6 to 10mmHg. Transitional and counterpulsation resulted in a double ventricular pulse and extended the duration of increased ventricular pressure, potentially impeding diastolic filling and coronary perfusion. This in vitro study showed the IVBP could restore the hemodynamic balance of a simulated SHF patient with dilated cardiomyopathy to healthy levels.

Autonomous origami: pre-programmed folding of inkjet printed structures

Self-folding, whereby a 2D net autonomously folds into a pre-ordained 3D shape when exposed to a stimulus, shows potential, in a manner similar to 3D printing, as a means of easily customisable digital manufacture. It also presents some inherent advantages over conventional additive manufacturing techniques, such as the low cost associated with mass-production of polymer sheets and coatings, the compatibility with most planar manufacturing techniques, and the ease of storage and transportation. A self-folding mechanism was developed by inkjet printing silver nanoparticle suspensions onto polyethylene terephthalate (PET) sheets. By providing sufficient electrical power to the printed tracks, resistive heating causes folding to occur along the printed silver lines. A bilayer strip model was adapted to analyse the steady-state fold angle of the PET substrate, which shows good qualitative agreement, and reasonable quantitative agreement, with the experimental data. Furthermore, inkjet-printed silver tracks are known for a significant reduction in resistivity as the sintering temperature increases. Therefore, a power control system that utilises a real-time resistance sensor was developed to enable power reference tracking. The developed mechanism was able to achieve folds up to 90° and a fast actuation time of 35 s when 2.25 W was provided to a 3 mm by 40 mm silver track.

Rapid and low power laser actuation of sputter-deposited NiTi shape memory alloy (SMA) MEMS thermal bimorph actuators

NiTi SMA thermal bimorph actuators have potential as high-force, high-displacement MEMS actuators. Historically, even microscale SMA actuation response has been limited to a maximum of ˜100 Hz. As NiTi film and device dimensions are scaled down into the micro and nano scales, heat transfer, and thus device cycling speeds can be significantly improved upon. We have used an in-situ annealed nickel-titanium (NiTi) shape memory alloy (SMA) sputter deposition process to sputter equiatomic NiTi films at 600 °C. We characterized our thin film (270 nm NiTi – 1.6 μm NiTi) material and verified its reversible shape memory effects (SME) using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and wafer bow versus temperature measurements. Upon release, the NiTi material exhibited a reversible phase change around 60 °C with a hysteresis of ˜3 °C. For the substrate confined case (i.e. NiTi on Si or Pt), hysteresis was much larger (i.e. ˜40 °C) with the phase change completed at ˜80 °C. In addition to SMA material characterization, we fabricated NiTi/Pt bimorph actuators at several (100 nm to 1.2 μm) NiTi and Pt thicknesses. Free-standing bimorph actuators were produced via a dry etch release, and temperature dependent curvature of these cantilevers was investigated. To address the low power, and high response time aspects, we performed a dynamic characterization using a 440 mW, 532 nm “green” laser to irradiate devices from 2 to 24 W/cm2 while measuring actuation response times that varied from 3 ms at the highest irradiation fluxes to 240 ms at the lowest. Our results showed decreased actuation powers and faster heating or actuation times compared to past works with NiTi microactuators. The NiTi films with 600 nm thickness on top of 20 nm Pt films exhibited the greatest change in curvature from 200 μm to flat states, and actuated in under 3 ms due to the very small volume of SMA requiring to be heated. These results suggest that NiTi/Pt bimorphs have potential applications as lower-power, faster-response, laser-activated micro shutters or thermal switches without needing a traditional wired power source.

Output feedback [formula omitted] control for active suspension of in-wheel motor driven electric vehicle with control faults and input delay

In this paper, an output feedback H∞ controller is proposed for active suspension of an electric vehicle driven by in-wheel motors with actuator faults and time delay. The dynamic damping in-wheel motor driven system, in which the in-wheel motor is designed as a dynamic vibration absorber (DVA), is developed to improve ride quality and isolate the force transmitted to motor bearings. Furthermore, parameters of vehicle suspension and DVA are optimized based on the particle swarm optimization (PSO) to achieve better suspension performance. As some of the states such as the DVA velocity and unsprung mass velocity are difficult to measure, a robust H∞ output feedback controller is developed to deal with the problem of active suspension control with actuator faults and time delay. The proposed controller could guarantee the system’s asymptotic stability and H∞ performance, simultaneously satisfying the performance constraints such as road holding, suspension stroke, and actuator limitation. Finally, the effectiveness of the proposed output feedback controllers is demonstrated based on the quarter vehicle suspension model under bump and random road excitations.

Adaptive Fault-Tolerant Control of Uncertain Switched Nonaffine Nonlinear Systems With Actuator Faults and Time Delays

This paper addresses the adaptive fault-tolerant control (FTC) problem of uncertain switched nonaffine nonlinear systems with actuator failures and time delays. Unlike the literature employing the FTC methods, the novel nonlinear fault compensate function with adjustable parameter factor, whose norm is used for approximation with fuzzy logic systems, is constructed based on the mean value theorem. Accordingly, a standard transformation scheme from the multi-input and single-output nonaffine nonlinear system to the corresponding affine nonlinear system is first to be given; then, the designed adaptation mechanism with state-dependent switching strategy can effectively eliminate the effects of multiple time delays and actuator faults, including outage and stuck modes. Furthermore, by using the Lyapunov–Krasovskii stability analysis method, it is proved that the proposed adaptive switched controller can guarantee the states of the overall closed-loop systems to asymptotically converge to zero. Finally, the simulation results are displayed to verify the feasibility of the presented approach.

Constrained H∞ control for a half-car model of an active suspension system with actuator time delay by predictor feedback

In this paper, constrained memory state-feedback H∝ control for a half-car model of an active vehicle suspension system with input time-delay in the presence of external disturbance has been investigated. Its prime goal is to improve the inherent trade-offs among power consumption, handling performance, ride quality, and suspension travel. The tire deflections and the suspension deflections are constrained by their peak response values in time domain using the generalized H2 (GH∝) norm (energy-to-peak) performance, while the ride comfort performance of the suspension system is optimized by notion of the H∝ control (energy-to-energy) to measure the body accelerations including both the heaving and the pitching motions. Similar to the well-known prediction-based methods, the prediction vector of the system is achieved to construct the memory state-feedback controller. Using the prediction vector, sufficient conditions guaranteeing closed-loop system stability as well as disturbance attenuation are obtained as some delay-dependent linear matrix inequalities (LMIs). In addition, some LMIs are added to limit the gain of the controller. In the case of feasibility, obtained LMIs provide the stabilizing gain of the memory controller. The proposed approach is applied to a half-car model of an active suspension system considering the actuator time-delay to illustrate the effectiveness of the proposed method.

Design of Elastomer-CNT Film Photoactuators for Nanolithography.

Polymer pen lithography (PPL) is an approach to multiplexing scanning probe lithography, in which an array of probes on a compliant film-coated rigid substrate are used to write patterns on a surface. Recently, it was shown that these nominally passive pen arrays can be rendered photo-active by making them out of a polydimethylsiloxane (PDMS)–carbon nanotube (CNT) composite. While such photoactuated pens in principle represent a rapid, maskless, and versatile nanomanufacturing strategy, a key challenge that remains is learning how to effectively control the writing of each pen, individually. In this research, we studied the design of PDMS–CNT thin-film photoactuators and experimentally explored the role of illumination radius, film thickness, and CNT concentration. Additionally, we have proposed a model that predicts actuation efficiency, actuation time, and the crosstalk between pens. Based upon these results, we have generated a map of working efficiency to elucidate the ideal choice for specific actuation requirements. This work lays the foundation for studying further photoactuatable composite films as actuators in applications beyond lithography including soft robotics and adaptive optics.

Accident analysis with MELCOR-fusion code for DONES lithium loop and accelerator

Safety assessment is a key issue for the licensing of DONES facility, the DEMO-Oriented Neutron Source. A first phase of the safety assessment includes Failure Mode Analyses of systems to identify postulated initiating events (PIEs), while deterministic accident analyses are lately performed to estimate source terms in radiological hazards. In addition, the deterministic analyses are also the basis to identify safety class structures, systems and components, and to establish the operational range of system parameters as well as the actuation of the protection system. In this paper two accident scenarios, previously identified as PIEs, are explored with the fusion version of the MELCOR 1.8.6 code. A loss of flow (LOFA) in the lithium loop due to the trip of the electromagnetic pump and a loss of vacuum (LOVA) in the accelerator beam duct due to containment rupture have been studied to provide a preliminary estimation of the available actuation time for detection and mitigation systems with a particular focus on the beam shutdown system and isolation of the vacuum duct.

Bifurcation-based embodied logic and autonomous actuation

Many plants autonomously change morphology and function in response to environmental stimuli or sequences of stimuli. In contrast with the electronically-integrated sensors, actuators, and microprocessors in traditional mechatronic systems, natural systems embody these sensing, actuation, and control functions within their compositional and structural features. Inspired by nature, we embody logic in autonomous systems to enable them to respond to multiple stimuli. Using 3D printable fibrous composites, we fabricate structures with geometries near bifurcation points associated with a transition between bistability and monostability. When suitable stimuli are present, the materials swell anisotropically. This forces a key geometric parameter to pass through a bifurcation, triggering rapid and large-amplitude self-actuation. The actuation time can be programmed by varying structural parameters (from 0.6 to 108 s for millimeter-scale structures). We demonstrate this bioinspired control strategy with examples that respond to their environment according to their embodied logic, without electronics, external control, or tethering.

Dynamic modeling and characteristic analysis of piezoelectric rudder actuator.

In this note, dynamic equations of the piezoelectric rudder actuator are established using a numerical method, and the dynamic characteristics are analyzed. A simulation is performed using finite element software to verify the validity of the theory. The results show that an increase in axial force has significant amplification effects on the static displacement output of the bimorph and its rudder actuator, and the axial stiffness of the piezoelectric bimorph is evidently nonlinear against larger axial force. The response time of the rudder actuator is less affected by the axial force and remains in the order of milliseconds under the axial force of 0.85 times the buckling critical load.

Probabilistic robust design of control systems for high-fidelity cyber–physical testing

Cyber–physicalempirical methods consist in partitioning a dynamical system under study into a set of physical and numerical substructures that interact in real-time through a control system. In this paper, we define and investigate the fidelity of such methods, that is their capacity to generate systems whose outputs remain close to those of the original system under study. In practice, fidelity is jeopardized by uncertain and heterogeneous artefacts originating from the control system, such as actuator dynamics, time delays and measurement noise. We present a computationally efficient method, based on surrogate modelling and active learning techniques, to (1) verify that a cyber–physical empirical setup achieves probabilistic robust fidelity, and (2) to derive fidelity bounds, which translate to absolute requirements to the control system. For verification purposes, the method is first applied to the study of a simple mechanical system. Its efficiency is then demonstrated on a more complex problem, namely the active truncation of slender marine structures, in which the substructures’ dynamics cannot be described by an analytic solution.

From two-dimensional to three-dimensional structures: A superior thermal-driven actuator with switchable deformation behavior

Inspired by origami, 3D structures constructed from 2D structures have increasingly attracted attention, which have potential applications in many fields. Herein, a novel double-layered actuator was fabricated by adding different thermo-responsive thermal expansion microspheres, expanding at low temperature (L-TEMs) and at high temperature (H-TEMs), into different silicone rubber layers. Due to the expansion of L-TEMs and H-TEMs at 120 and 170 °C, respectively, the active and passive layers could exchange at different temperatures, showing switchable deformation behavior. Compared with traditional double-layered actuators, the actuator with the switchable active layers is capable of providing additional functionality. The two layers were assembled by crosslinking the silicone rubber at the interface of the two layers, which endows the good stability of the double-layered actuator. The 2D double-layered structures of the actuators could be transformed into complex 3D structures by heating. In addition, the actuation time was shortened by adding 50 phr alumina due to the enhancement of thermal conductivity and the limited increase in Young’s modulus. This work could pave a way to the design and preparation to high-performance actuators with multiple functions.

Fault-Tolerant Control for Wing Flutter Under Actuator Faults and Time Delay

Investigating the design of the controller stabilizing the wing flutter system, which is robust against actuator faults, actuator saturation, time delay, parameter uncertainties and external disturbances. The model of the wing flutter system that considered the effects of actuator faults and saturation, time delay, parameter uncertainties and external disturbances is constructed by the Lagrange method. Then the finite-time fault-tolerant controller is derived, the stability of which is proved by the Lyapunov function. The simulation results elucidate that, the proposed fault-tolerant controller can handle the actuator faults effectively, meanwhile the wing flutter of the reentry vehicle can be suppressed instantly. The robustness of the actuator against actuator saturation, time delay, parameter uncertainties and external disturbances is also demonstrated.

Shape memory alloy–actuated prestressed composites with application to morphing automotive fender skirts

This work presents smart laminated composites that enable morphing vehicle structures. Morphing panels can be effective for drag reduction, for example, adaptive fender skirts. Mechanical prestress provides tailored curvature in composites without the drawbacks of thermally induced residual stress. When driven by smart materials such as shape memory alloys, mechanically-prestressed composites can serve as building blocks for morphing structures. An analytical energy-based model is presented to calculate the curved shape of a composite as a function of force applied by an embedded actuator. Shape transition is modeled by providing the actuation force as an input to a one-dimensional thermomechanical constitutive model of a shape memory alloy wire. A design procedure, based on the analytical model, is presented for morphing fender skirts comprising radially configured smart composite elements. A half-scale fender skirt for a compact passenger car is designed, fabricated, and tested. The demonstrator has a domed unactuated shape and morphs to a flat shape when actuated using shape memory alloys. Rapid actuation is demonstrated by coupling shape memory alloys with integrated quick-release latches; the latches reduce actuation time by 95%. The demonstrator is 62% lighter than an equivalent dome-shaped steel fender skirt.

ASTHMA CONTROL EVALUATED WITH ELECTRONIC MEDICATION MONITOR (EMM)-DEFINED OCCASIONS OF SHORT-ACTING BETA-AGONIST INHALER USE

Introduction The Global Initiative for Asthma (GINA) and National Heart Lung and Blood Institute Expert Panel-3 (EPR-3) guidelines quantify short-acting beta-agonist (SABA) use in their assessment of asthma control. Both define control by the number of SABA uses/week, but neither defines the duration for each “occasion” of use. Utilizing EMMs, we compared estimates of asthma control using GINA and EPR-3 criteria based on 3 potential occasion definitions of SABA. Methods Data were collected from 5,067 adults from 2015-2017 with self-reported asthma and an EMM-equipped SABA inhaler to passively collect time and date of SABA actuations. For GINA, partly controlled (PC) asthma was use >2 times/week. For EPR-3, not well-controlled (NWC) was use >2 days/week, and very poorly controlled (VPC) was use several (≥3) times a day. Using EMMs, 3 occasions of SABA use were studied as ≥1 puff of SABA within 2-, 4- or 6- hour durations. This study was exempted from IRB approval. Results Both GINA and EPR-3 criteria identified 34-37% of patients as PC or NWC irrespective of occasion definition. Among those NWC based on EPR-3 criteria, the prevalence of VPC was 50%, 44% and 32% with 2-, 4- or 6-hour occasions, respectively. Conclusions The prevalence of very poorly controlled asthma varied by the duration of an occasion. Standardized definitions of an occasion and collection of SABA data with EMMs should be harmonized to more accurately assess asthma control and identify patients who may need modifications in controller therapy to achieve optimal control.

Modified L1 Adaptive Control Design for Satellite FMC Systems with Actuators Time Delay

A modified method for satellite attitude control system in presence of novel actuators is proposed in this paper. The attitude control system is composed of three fluidic momentum controller (FMC) actuators that are used to control Euler angles and their dynamics is considered in satellite attitude equations as well. L1 adaptive control is utilized for satellite three-axial stabilization. A significant characteristic of L1 adaptive control structure is that robustness is guaranteed in presence of fast adaptation. The main achievement of this controller is that the error norm is inversely proportional to the square root of adaptation gains. Therefore, large values of gains provides some advantages. The proposed L1 adaptive control is designed based on simplified attitude dynamic equations without satellite coupling effects, and then it is placed on coupled nonlinear equations. Next, the impact of available delay on FMC actuators is investigated. Simulation results suggest that the system remains stable with the assumption of actuators time delay, but it experiences some oscillations in Euler angles, control inputs and angular velocities. In order to solve this problem, a modified L1 adaptive control system including a predictive observer with high estimation speed is used. Finally, it is recognized that the available oscillations are reduced even when the actuator time delay increases and thus the control system’s performance improves.

Altering gait variability with an ankle exoskeleton.

Exoskeletons can influence human gait. A healthy gait is characterized by a certain amount of variability compared to a non-healthy gait that has more inherent variability; however which exoskeleton assistance parameters are necessary to avoid increasing gait variability or to potentially lower gait variability below that of unassisted walking are unknown. This study investigated the interaction effects of exoskeleton timing and power on gait variability. Ten healthy participants walked on a treadmill with bilateral ankle-foot exoskeletons under ten conditions with different timing (varied from 36% to 54% of the stride) and power (varied from 0.2 to 0.5 W∙kg-1) combinations. We used the largest Lyapunov exponent (LyE) and maximum Floquet multiplier (FM) to evaluate the stride-to-stride fluctuations of the kinematic time series. We found the lowest LyE at the ankle and a significant reduction versus powered-off with exoskeleton power (summed for both legs) of 0.45 W∙kg-1 and actuation timing at 48% of the stride cycle. At the knee, a significant positive effect of power and a negative interaction effect of power and timing were found for LyE. We found significant positive interaction effects of the square of timing and power for LyE at the knee and hip joints. In contrast, the FM at the ankle increased with increasing power and later timing. We found a significant negative effect of power and a positive interaction effect of power and timing for FM at the knee and no significant effects of any of the exoskeleton parameters for FM at the hip. The ability of the exoskeleton to reduce the LyE at the ankle joint offers new possibilities in terms of altering gait variability, which could have applications for using exoskeletons as rehabilitation devices. Further efforts could examine if it is possible to simultaneously reduce the LyE and FM at one or more lower limb joints.

Competência profissional dos trabalhadores de programas de atividade física da atenção básica à saúde de Pernambuco


 
 
 O objetivo do estudo foi verificar a associação entre as competências profissionais de conhecimento, habilidade e atitude autopercebidas com a formação inicial, continuada, educação permanente e atuação profissional em programas de promoção da atividade física (PPAFs) na atenção básica à saúde de Pernambuco. Estudo transversal com 553 trabalhadores de 132 cidades. Competência profissional foi mensurada por 23 questões, com escala tipo likert nas dimensões de conhecimento (n = 7), habilidade (n = 9) e atitude (n = 7). Informações sociodemográficas, de tempo de atuação, formação inicial, continuada e educação permanente foram as variáveis independentes. O teste k-means não hierárquico foi utilizado para identificar grupos com maior e menor percepção de competência a partir do Z-scores do conhecimento, habilidade e atitude. Regressão logística binária bruta e ajustada foi utilizada para identificar os fatores associados a maior percepção de competência. Um total de 66,4% tinham formação em Educação Física, com menor quantidade de experiências durante a formação inicial e continuada. Ter formação superior (OR = 2,21; IC95%: 1,04-4,68), em Educação Física (OR = 2,48; IC95%: 1,47-4,85), ser servidor público (OR = 1,86; IC95%: 1,13-3,27) e participar de cursos, eventos e capacitações em atividade física no último ano ofertados pela gestão (1 - 2 cursos; OR = 3,86; IC95%: 2,17-6,81 e ≥ 3 cursos; OR = 4,27; IC95%: 1,99-7,58) aumenta a chance de percepção de maior competência. É necessário um redirecionamento na formação inicial, implementação de uma política de capacitação continuada com o foco na atenção básica de saúde, bem como a valorização do profissional fortalecido pelo tipo de vínculo.